Endoscopic surgical instruments are often preferred over traditional open surgical devices since a smaller incision tends to reduce the post-operative recovery time and complications. Consequently, significant development has gone into a range of endoscopic surgical instruments that are suitable for precise placement of a distal end effector at a desired surgical site through a cannula of a trocar. These distal end effectors engage the tissue in a number of ways to achieve a diagnostic or therapeutic effect (e.g., endocutter, grasper, cutter, staplers, clip applier, access device, drug/gene therapy delivery device, and energy device using ultrasound, RF, laser, etc.).
Positioning the end effector is constrained by the trocar. Generally these endoscopic surgical instruments include a long shaft between the end effector and a handle portion manipulated by the clinician, this long shaft enables insertion to a desired depth and rotation about the longitudinal axis of the shaft, thereby positioning the end effector to a degree. With judicious placement of the trocar and use of graspers, for instance, through another trocar, often this amount of positioning is sufficient. Surgical stapling and severing instruments, such as described in U.S. Pat. No. 5,465,895, are an example of an endoscopic surgical instrument that successfully positions an end effector by insertion and rotation.
Depending upon the nature of the operation, it may be desirable to further adjust the positioning of the end effector of an endoscopic surgical instrument rather than being limited to insertion and rotation. In particular, it is often desirable to orient the end effector at an axis transverse to the longitudinal axis of the shaft of the instrument. The transverse movement of the end effector relative to the instrument shaft is conventionally referred to as “articulation”. This articulated positioning permits the clinician to more easily engage tissue in some instances. In addition, articulated positioning advantageously allows an endoscope to be positioned behind the end effector without being blocked by the instrument shaft.
While the aforementioned non-articulating stapling and severing instruments have great utility and may be successfully employed in many surgical procedures, it is desirable to enhance their operation with the ability to articulate the end effector, thereby giving greater clinical flexibility in their use. To that end, the four above cross-referenced applications disclose use of a rotational motion to articulate an end effector of a surgical stapling and severing instrument. A clinician rotates an outer control at the base of the shaft of the instrument to effect this articulation. In other articulating surgical instruments, articulation is generally effected by a longitudinal or rotational control input that is transferred as a longitudinal movement to the articulation joint. For instance, U.S. Pat. No. 6,241,139 describes a rotary control operably coupled to a stepped cam driver slot. Rotary motion of the control moves an intermediate piece containing the stepped cam driver slot laterally to articulate the end effector.
While these articulation controls do perform the intended function, it is believed that an enhanced articulation control may provide additional benefits. For instance, it would be desirable if the visual indication and tactile feel provided by the articulation control were intuitively understood by the clinician as to the expected direction and amount of articulation. In addition, it would be further desirable that the articulation control readily accept adjustment by the clinician yet resist a force on the end effector that may inadvertently change the amount of articulation. Furthermore, it would be further desirable that some versions of the articulation control be particularly suited for a surgical stapling and severing instrument that has a rotational motion down the shaft to effect articulation.
Consequently, a significant need exists for an improved articulation control for a surgical instrument.